At the old castle library, Twilight suggests sorting the books by category, but Starlight says they should be sorted by age. As Spike picks up a book about ferocious Everfree Forest flora, a vine-like plant expels dust in his face, causing him to sneeze fire. Before he burns all the books in the library with his dragon breath, Twilight and Starlight suggest he find another, less dusty room to sort books in, and Spike takes some of his favorite comic books with him as he leaves. He soon settles in a castle corridor lines with pony suits of armor.

Back in the library, Twilight and Starlight continue to argue over how the books should be sorted. Throughout their arguing, more vine creatures appear to spread their dust spores, much to Owlowiscious' alarm. Their growth soon spreads over the stone dragon statues that line the castle. Meanwhile, Spike takes a break from his comic books to continue reading the book on ferocious flora, and he discovers information about the vines growing around the castle.

Owlowiscious finally stops Twilight and Starlight's arguing and alerts them to the threat that grows around them. Spike dashes into the library, being chased by vines and living suits of armor, and explains that the vines are trying to destroy the ferocious flora book. Starlight fends off the attacking plants and shields herself and her friends in a force field while Twilight reads about the vines in the book, learning that their spores causes agitation in ponies and they feed on competitive hostility.

Twilight and Starlight try to fight off their negative and hostile emotions, but the vines have fed on enough of them to grow into a large beast made of plants and rocks. As the vines start to penetrate Starlight's force field, Twilight tells her to buy some time so she can find a counter-spell. Using a spell she learned earlier that day, Starlight makes herself, Spike, and Owlowiscious grow to immense size, and they fight off their attackers with brute force.

Before long, Twilight finally finds an incantation to focus her and Starlight's magic: "From both of us together, together we're friends... If we understand each other, our great strengths will blend." Twilight and Starlight use this incantation to balance out their emotions. With no more hostility to feed on, the vines become weak, allowing the four friends to drive them off. As the vines slither away into the forest, Starlight, Spike, and Owlowiscious return to normal size.

Twilight and Starlight learn from the ferocious flora book, which was apparently written by Star Swirl himself, that the vines—called "squirm-spores"—are an ancient monster that was drawn by the energy of the book and wanted to destroy Star Swirl's spell. Star Swirl had previously fended off the beast with the help of Melvin the manticore. Realizing cooperation was the only way to defeat the squirm-spore, Starlight and Twilight apologize for their earlier arguing, and they commend each other for their talents displayed.

With all other distractions now dealt with, Twilight and Starlight go back to sorting the castle's books—by age, as Starlight originally suggested.

Quotes

Spike: I love presents as much as anyone, Twilight, but Hearth's Warming Eve is months away... not that you can ever spend too much time planning gifts for me.

Twilight Sparkle: No peeking!

Starlight Glimmer: Finally, a break from friendship lessons! I've been trying to dig into this book for a week!

Twilight Sparkle: Oh, ok... I also thought we might find some ancient spells together, since Star Swirl the Bearded helped build the castle, but I can always tell you later if—

Starlight Glimmer: Star Swirl? ... Well, maybe I could use one more friendship lesson today.

Twilight Sparkle: ...And your village was certainly efficient, when you were bossing everyone around!

Starlight Glimmer: Now that's not a very friendly comment from a friendship teacher, and you think I'm the bossy one?

Twilight Sparkle: "From both of us together, together we're friends...

Starlight Glimmer: ...If we understand each other, our great strengths will blend."

Spike: That... was awesome! You totally have to make me giant the next time some monster invades Ponyville! I can—

Starlight Glimmer: Sorry, Spike. That spell only works one time per customer.

Spike: Awww! Rarity wasn't even here to see it! Although I guess that other time I turned giant, I kind of kidnapped her...

Twilight Sparkle: I guess I've been putting a lot of pressure on myself—on both of us—to trying to have all the right checklists and answers to be the best friendship teacher ever. But even Star Swirl didn't always know everything.

Starlight Glimmer: You are a great teacher! Maybe we can still learn from each other in some areas—like magic—but I want to keep learning from you when it comes to friendship... Maybe with a break once in a while...